ESR1 and carcinoma: Of these 45 patients, 88.9% of patients had invasive ductal carcinoma, 4.4% of patients had lobular carcinoma, and 6.7% of patients had carcinoma of other histology; 55.6% of patients were estrogen receptor (ER)-positive and 42.2% of patients were ER-negative; 40.0% of patients were progesterone receptor (PR)-positive, and 57.8% of patients were PR-negative; 1 patient (2.2%) had missing data for both ER and PR status; 11.1%, 26.7%, and 62.2% of patients had received 1, 2, and ≥ 3 regimens at last treatment, respectively (Table 1).